Chimere Mba-Jonas MD, Presenter: Nothing to Disclose

Charles Ross Schmidtlein PHD, Abstract Co-Author: Nothing to Disclose

Tunc Ali Iyriboz MD, Abstract Co-Author: Nothing to Disclose

Sinchun Hwang MD, Abstract Co-Author: Nothing to Disclose

To evaluate Metal Artifact Reduction Software (MARS) for improving Single-Source Dual-Energy CT (SSDECT) image quality in patients with hip metal hardware by measuring CT attenuation and its standard deviation (SD) of pelvic tissues as an indirect measure of image variability and comparing these with those of standard images.

The study included 100 SSDECT pelvic exams of patients with hip metal hardware: open-reduction internal-fixation (ORIF) (n=19), hemiarthroplasty (HA) (n=10), unilateral total hip replacement (UTHR) (n=48), bilateral total hip replacement (BTHR) (n=16), and combination of hardware (n=7). In standard and MARS images obtained at 110keV, mean CT attenuation values and its SD were measured in four tissue types, urinary bladder (ub), anterior acetabulum (aa), perirectal fat (pf), iliopsoas muscle (im), by placing a regions of interest (ROI). The SD represented the variability due to streak artifacts, where greater artifacts give a larger SD. Significance in difference of attenuation variability was measured using the Wilcoxon signed rank test.

There was a significant difference in CT attenuation values between standard and MARS images depending on types of hardware and pelvic tissues (p<0.001–0.05). SD’s of pelvic tissues except for pf were lower with MARS in HA, UTHR, BTHR (p<0.001–0.05) whereas SD’s of ub and im were lower with standard images in ORIF (p<0.01-0.02). The most significant difference in SD’s between standard and MARS images (p<0.001) were seen in UTHR; SD of ub, aa, im in standard images were 30±13, 106±77, 62±39 HU; in MARS images 25±9, 61±25, 33±15 HU respectively.There is no significant difference in SD of pf between standard and MARS images regardless of hardware types (P>0.05).

The reduction in CT attenuation variability achieved using MARS depends on both types of metal hardware and pelvic tissues; it is larger with HA, UTHR, BTHR but least in ORIF and perirectal fat.

It is important to consider types of metal hardware and tissue pathology prior to applying MARS in SSDECT because this technique is hardware and tissue-dependent.

Mba-Jonas, C, Schmidtlein, C, Iyriboz, T, Hwang, S, Comparing CT Attenuation Variability in the Pelvis After Hip Metal Hardware Placement Using Single-Source Dual-Energy CT Standard and Metal Artifact Reduction Software.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12034297.html